Combining alternating current channels with superposed telegraph circuits



Aug. 4, 1931. 1,817,702

\ COMBINING ALTERNATING CURRENT CHANNELS WITH SUPERPOSEDl TELEGRAl-'HCIRCUITS R. V. MORGENSTERN Filed May`l4, 1930 2 Sheets-Sheet l Aug. 4,1931. R. v. lvloRGl-:NSTER'N '1,817,702

COMBINING ALTERNATING CURRENT CHANNELS WITH SUPERPOSED TELEGRAPHCIRCUITS Filed May 14. 1930 2 Sheets-Sheet 2 gru/vento@ v www/yi.

Patented Aug. 4, 1931 UNITED STATES PATENT OFFICE RONALD V.MORGENSTERN,IOF IRVINGTON, NEW YORK, ASSIGNOR TO THE WESTERN UNIONTELEGRASPH COMPANY, OF NEW YORK, N. VY., A CORPORATION F -NEW YORKCOMBINING .ALTERNATING CURRENT CHANNELS 'WITH SUPERPOSED TELEGRAPHCIRCUITS Application filed May 14,

This invention relates to telegraph systems, and in articular to thecombination of an alternating current system with supervposed telegraphcircuits.

The object of the invention is to superpose an alternating currentchannel upon a direct current' telegraph circuit in such a Wayl as -toprevent the alternating current channel from interfering with the directcurrent channel. Specifically an alternating current carrier telegraphcircuit channel is superposed upon the side circuits of a superposedtelegraph system Without interference to either of the side circuits orto the superposed circuit.J

An object of the invention is to neutralize directly the alternatingcurrent interference to the physical or direct current telegraphcircuits.

A further object is to introduce the alternating current signalingchannel on to. the line Wires of a superposed group by means of theinductive shunt connected across the two points at which battery isapplied to the side circuits.

In a superposed A..C. carrier system according to this invention, thesystem can be made fairly rugged as compared With the ordinary carriersystem inasmuch as the frequencies which need to be employed will becomparatively low, and the amounts of power which can be employed fairlylarge. This is made possible because of the provision of means forneutralizing A. C. interference to the D. C. circuit by superposing uponthe D. C. circuit a portion of the A. C. signal just large enough toneutralize the disturbing A. C. .currents which leak into the directcurrent apparatus.

In certain superposed systems the superposed circuit is placed on thephysical or side circuits by means of a tap at the midpoint of' a shuntacross two points at which battery is applied to the side` circuits. Inaccordance with one method disclosed hereinafter, this shunt isconverted into a transformer the secondary of which is tapped to provideconnection of the superposed circuit thereto. The primary is connectedthrough 50 a code making device, illustrated as a key,

1930. serial No. 452,481.

to a source of alternating current of the desired frequency. As shown, acondenser is placed in series with the primary to tune the primarycircuit to resonate at the desired frequency.

At the receiving end of the alternating current channel the shunt towhich the superposed circuit is connected is changed to a transformer,connection of the superposed circuit being made to the electricalmidpoint of. the primary of the transformer. The tuned secondary circuitof this transformer isused to feed the inputcircuit of a vacuum tube,either directly or through the medium ofa second transformer. Asillustrated, in the drawing, an amplifier is employed. In

`the output circuit of the last tube of the amplifier circuit,that is,the tube preceding the detector tube,is inserted a transformer which iscoupled through a ci-rcuit of variable resistance to a coil of the sidecircuit receiving relay properly poled with respect to its other coils.The purpose of the resistance is to regulate or limit the strength ofthel am-l plilied signal current which is supplied to the neutralizingrelay coil.

Details of the invention will be disclosed more fully in connection withthe drawings i in Whicht- Y Figures 1-A and 1B, which when placedtogether form a complete continuous figure, show a superposed telegraphsystem in which one of the side circuits is used to transmit alternatingcurrent signals in one direction and the other side circuit to transmitalternating current signals in the opposite direction.

Figure 2 is a fragmentary View showing an alternative method of couplingthe alternating current channel to the metallic side circuit.

In Figures l-A and l--B the line conductors are represented at 1 and 2,the side circuit transmitter 3 being connected thereto by Way of afilter circuit diagrammatically represented at 4 and the line coils 5and 6 of a D. C. receiving relay 7. The side circuit transmitter isdiagrammatically represented as comprising a pair of generatorsconnected through resistance, in the usual manner, to the contacts andtongue of a code making device. The receiving relay 7 is connected inneutral relation to transmitter' 3 by means of Van artificial line 8 andcomprises the line coils 5 and 6 and an additional coil 9, the latterconnected in series in the artificial line. Points of the receivingrelay which are neutral with respect to the transmitter l3 are indicatedat l0 and 11. To these neutral points is connected an inductiveshunt 12at the electrical midpoint of which is tapped a conductor 85 by Way ofwhich superposed circuit terminal apparatus is conductively connected tothe side circuit. l

The principles in accordance with which this shunt circuit may bedesigned are disclosed in an application of R. V. Morgenstern Serial No.258,948, entitled Superposed telegraph circuit-s, filed March 3, 1928.The resistance and inductance of the shunt circuit lare adj usted to'give the least distortion of the received signals at the distant end ofthe circuit. The shunt circuit has no harmful effect upon the signalcurrents from transmit" ter 3 and yet provides means for connecting thesuperposed circuit to the two points to which battery is applied on theside circuit.

In accordance with the principles of this invention, the inductiveportion of shunt 12 comprises a transformer secondary 13, the prlmary 14of which is connected to the alternating current source 15 through acode making device schematically represented by the key and contacts 16.An adjustable condenser 17 in series withthe primary 14 tunes thecircuit to the frequency of the alternating current source 15.

At the receiving end of the'line 1-2 is .found direct current apparatuscorrespondlng-to that already described. A transmitter 18 isschematically represented by a tongue having alternate contacts throughwhich current impulses of opposite lpolarity are supplled from a pair ofgenerators and their associated resistances. The D. C. signal current issupplied to line through a filter 19 and the coils 20 `and 21 of areceiving relay 22. A third coil 23 of the relay is connected in serieswith the artificial line 24.- A shunt circuit 25 is connected to neutralpoints 26 and 27 of the receiving relay, the inductive port-ion of whichcomprises a transformer having a. primary 28 and secondary 29. Aconductor 30, connected to the electrical midpoint of the primary 28leads to superposed 1c1rcu1t terminal apparatus indicated generaly at31. f 4

Secondary 29 of the shunt circuit trans- I former leads to a couplingtransformer 32 by way of a series condenser 33. The condenser 33 may beadjusted to tune the circuit to the frequency of the alternatingcurrent. source 15.

The secondary 32 of the coupling transformer is connected to the inputof a threeelectrode thermionic vacuum tube 34. The

Lerares output circuit of vacuum tube 34 is tuned to the frequency ofthe received A. C. signals and is inductively connected by anothercoupling transformer 36 to a second amplifier stagecomprising amplifyingtube 37. The output circuit of vacuum tube 37 includes a tuned circuit38 coupled to the input of a detector tube 39. Tube 39 suppliesrectified signal current to a receiving relay for the A. C. carriercircuit.

The coils 20, 21 and 23 of the receiving relay 22 are shown providedwith by-pass condensers 45, 46 and 47 respectively, but these by-passcondensers may be omitted if desired.

54 and 55 of a D. C. receiving relay 56. Tov

Aneutral points of the relay is connected a shunt circuit 57 tapped atits electrical midpoint by a conductor 58 which leads tothe superposedcircuit terminal apparatus 31 hereinbefore referred to.4 The transformer59 in shunt 57 supplies alternating current signals to the shuntandthence to the side circuit from an alternating current generator 60. Akev 61 in series with tuning condenser 62 completes the circuit of theA. C. generator.

At the other terminal of the side circuit 50, 51, D. C. terminalapparatus comprises a transmitter 63 connected to the line through afilter 64 and the line windings 65 and 66 of a D. C. receiving relay 67The line windings of the relay and its artificial line winding are shownshunted by by-pass condensers, but this feature is optional. One purposeof the by-pass condensers is to cut down the amount of A. C. signalingcurrentl which passes through the windings of the D. C. rela Ti; neutralpoints of the receiving relay 6 is connected the shunt 68 at theelectrical center of which a conductor 69 leads to superposed circuitterminal apparatus 70. The transformer 71 in shunt circuit 68 forms partof an intermediate circuit 72 tuned to the frequency of the alternatingcurrent ofthe transmitting generator 60. Thetuned intermediate circuitsupplies received alternating current signals to the grid circuit of avacuum tube 75 by way of the coupling transformer 74.

The tuned outputl circuit 76 of tube 75 is coupled inductively to thegrid circuit of a second amplifier tube 77. The output circuit ofamplifier tube 77 includes the transformer 78 and a loop tuned circuit79. Tuned circuit 79 is coupled to the grid circuit of detector tube 80in the output circuit of which is connecteda receiving relay 81 for thealternating current circuit.

In Figure 2 is shown an alternative method for connecting thealternating current channel to the inductive resistance shunt. In thisfigure the conductors of the side circuit are represented as and 91, theline windings of the D. C. relay at 92 and 93, the `artificial line at94, and the artificial line winding of the D. C. relay at 96.Transmitter 97 is connected through a filter 98 to neutral points of therelay. To these same neutral. points is connected a shunt circuit 99. Inthis case the shunt circuit 99 comprises two portions in parallel. One.portion includes the two electrically equal halves 100 and 101 of aninductive resistance shunt, at the electrical midpoint 102 of whichconnection may be made to a superposed circuit. The other portioncomprises a coupling transformer 103 including two windings 104 and 105.The winding 104 is in parallel to the inductive resistance shunt. Thewinding 105 is connected to the apparatus of the alternating currentchannel.

An arrangement according to Figure 2 may be employed where theresistance and inductance of the shunt are such that the shunt cannotreadily be converted into a suitable transformer. It may also be used inthe case of superposed systems such as that disclosed in the applicationof Morgenstern & Teter, Serial No. 422,194 filed January 20, 1930,entitled Superposed telegraph system, in which the superposed circuit istaken out of the center of the armature of a generator forming thesignaling source on the side circuit. Y

It is to be understood that the alternative connection illustrated inFig. 2 may be used at either end of either side circuit; that is, it maybe used in place of the shunt circuits indicated at 12, 25, 57 and 68,or at any one or more of these. If the circuit of Fig. 2 replaced theshunt 12 or the shunt 57, then the coil 105 of Fig. 2 would be connectedto alternating current transmitting apparatus. If the shunt circuit ofFig. 2 replaced the shunt 25 or 68, the coil 105 of Fig. 2 would beconnected to alternating current receiving apparatus.

The filter circuits represented diagrammatically at 4, 19, 53 and 64 maybe parallel resonant circuits tuned to the frequency of thecorresponding alternating current generator or they may be low-passfilters designed to transmit alternating current of the signalingfrequency and to exclude undesired components of the direct currentsignal. Any other form of filter accomplishing vthe desired purpose maybe used.

By selecting the frequency of the alternating current channel in properrelation to the frequency components of the transmitted signal from thedirect current sources of the side circuit, the interference betweencircuits can be minimized and the effect of the added filter apparatuson the side circuits can also be minimized. v

The condensers in parallel with the coil of the receiving relay 22 (e.g. 45, 46 and 47) at the receiving end of the A. C. channel may beproportioned with relation to the inductance of the relay coils and thefrequency of the alternating current channel to reduce both the amountof interference current to be neutralized and the impedance of the D. C.relay to the alternating current. This current from the alternating.current channel which passes through the relay coils tends to cause itto operate. By passing the correct amount of current through theneutralizing relay coil in the amplifierl circuit, this current from thealternating current channel may be neutralized.

Although but one alternating current channel is shown on the drawing,additional channels may be employed if proper apparatus be provided toseparate them.

The frequency supplied from the alternating current source 15 and thatsupplied from the alternating current source 16 need not be the same. Ashas been pointed out above, the frequencies may be comparatively low andthe amounts of power employed may be fairly large since interference tothe physical or direct current telegraph circuit can be neutralizeddirectly intsead of depending upon filters to separate the directCurrent and alternating current channel. In this connection it will benoted that the alternating current channel is applied to the sidecircuits at the same point as the D. C. signaling potential from theseside circuits.

Itis apparent that the alternating current chanel may be superposed on aside circuit operating in one direction only instead of duplex.

The parallel resonant tuned circuit or low pass filter inserted in thebattery supply circuit of the side circuits serves to minimize theshunting effect of the direct current battery supply of the sidecircuits on the alternating current channel, as Well as to minimize theinterference from the direct current chinnels into the alternatingcurrent channe s.

The alternating current porton of the system is prevented frominterfering with the direct current portion as follows. the key 16connects the source of alternating current 15 to the tuned circuitcomposed of condenser 17 and transformer primary 14. The alternatingcurrent then passes via transformer secondary 13 which forms a part ofshunt circuit 12 topoints 10 and 11 of the receiving relay 7 on thedirect current circuit connected to line wires 1 and 2. The alternatingsignaling current has two paths betweenpoints 10 and 11. One path,visvia Closing 1.

:ias

coil 23 and artificial line 24.

artificial line coil 19 of relay 7 and the artificial line 8. The otheris via coil 5 of relay 7 'line wire 1, the transformer primary 23 (whichforms a. part of shunt circuit 28) coil 21 of relay 22, line wire 2 andcoil 6 of relay 7. A small ortion of the current will pass betweenpoints 26 and 27 of relay 22 Via relay The filter 19 stops thealternating current from flowing via the transmitter 18.

Now consider the effects of the alternating current from source 15 onthe receiving relays 7 and 22 of the direct current circuit. Coils 5 and6 are connected to line wires 1 and 2 in series aiding and are connectedin opposition to relay coil 19 in series with the artificial line 8.Coils 5 and 6 together have the same number of turns as relay coil 19.

If, then, the artificial line circuit has the same effective im edanceas the real line at the frequency of tlie alternating current channel,the same current will pass through coil 19 of relay 7 as through coils 5and 6 and in opposite directions, and relay 7 will not be affected byoutgoing alternating current, just as it is not affected by current fromthe direct current transmitter 3.

Current from the alternating current channel passes through coils 20,21and 23 of relay 22 in a direction to cause relay 22 to tend to operate.

Relay 22 is, however, equipped with coil 44 which is connected throughadjustable resistance 44 and transformer windings 42 and 41 to theoutput circuit of vacuum tube 37. The alternating current in the relaycoil 44 is adjusted in amount and phase relationship to neutralize theeffect of that coming over line wires 1 and 2 and passing through thecoils 20, 21 and 26 of relay 22. If necessary to get\the proper phaserelationship, a variable condenser can be placed in the circuitcontaining neutralizing .coil 44.

Alternating current from source 60 is prevented from interfering withrelays 56 and 67 connected to wires 50 and 51 in the same manner. Thatis, the effect on relay 56 is balanced out by the artificial line andits associated relay coil. The effect on relay 67 is balanced out bymeans of the neutralizing coil 83 and its associated circuit.

I claim:

1. In a signaling system, a line circuit comprising a pair ofconductors, a source of D. C. Voltage connected across terminals of saidline to apply direct current signals thereto, an inductive shuntconnected across said terminals with a superposedcircuit connected tothe electrical midpoint of said shunt and a source of A. C. voltageconnectedl to apply A. C. signal currents to said line circuit at saidterminals.

2. In a signaling system a line and a balancing line arranged for duplexoperation, a transmitter, relay windings in said line and balancing lineconnected so that the relay is in neutral relation with respect to saidtransmitter, a circuit in shunt to said transmitter, a` sgiperposedcircuit connected to said line by way of said shunt circuit, analternating current signal receiving circuit connected to said shunt andmeans for applying a portion of the signal energy in said receivingcircuit to anadditional relay winding whereby said relay is neutral wthrespect to said alternating current signals.

3. A signaling circuit comprising a line, a D. C. signal transmitter anda D. C. rcceiving relay connected to said line so that thel relay isneutral with respect to D. C. signals from said transmitter, aninductive shunt cfr cuit connected across said D. C. transmitter, asuperposed circuit connected to said line at an intermediate point insaid shunt circuit, an alternating current receiving circuit connectedeffectively in parallel to said shunt and means interconnecting saidreceiving circuit and said D. C. relay for neutralizing the effect ofalternating current signals on said D. C. relay.

4. A signaling circuit comprising a line, D. C. transmittin andreceiving apparatus connected to said l1ne to provide duplex operationthereover, inductive shunt circuits in parallel to said line across saidD. C. transmitting apparatus, an alternating current source coupled toone of said shunt circuits for applying A. C. signals to said line, analternating current receiving circuit coupled to the other shunt circuitand means interconnecting said alternating receiving circuit and itsassociated D. C. receiving apparatus for applying a portion of the A. C.signal current to said D. C. receiving apparatus.

5. A signaling circuit comprising a line, D. C. transmitting andreceiving apparatus connected across the line at both terminals thereofto provide duplex operation. thereover, inductive shunt circuits inparallel to said line across said D. C. transmitting apparatus, analternating current source coupled to one of said shunt circuits forapplying A. C. signals to said line, a tuned alternating currentreceiving circuit coupled to the other shunt circuit, by-pass condensersin shunt to said D. C. receiving apparatus and means interconnectingsaid alternating current receiving circuit and the D. C. receivingapparatus at the same terminal for applying an adjustable portion of thereceived A. C. signal current to said D. C. receiving apparatus.

6. A signaling circuit comprising a line, D. C. transmitting andreceiving apparatus connected across the line at each terminal thereofto provide duplex operation thereover, inductive shunt circuits inparallel to said line across said D. C. transmitting apparatus, analternating current source coupled to one of said shunt circuits forapplying A. C. signals to said line, a tuned alternating currentreceiving circuit coupled to the other shunt circuit and filtering meansin series with said D. C. transmitting apparatus across the line havinga frequency characteristic designed to exclude currents of the frequencyof the alternating current source, whereby the shunting action of saidD. C. transmitter to A. C. signal currents and interference from said D.C. transmitter in the A. C. receiving channel are suppressed.

7. A signaling circuit comprising a line, a D. C. telegraph transmitterconnected across said line, an inductive shunt circuit connected to theline terminals of said transmitter having electrical constants such thatthe shunting action of the inductive circuit to signal currents ofopposite polarities from said transmitter are practically suppressed atthe beginning of a signal, and a tuned alternating current signalreceiving circuit coupled to said shunt effectively in parallel to theterminals thereof.

8. A signaling circuit comprising a line, a D. C. telegraph transmitterconnected across said line, a D. C. receiving relay having windings inseries in said line, an inductive shunt circuit connected to the line.terminals of said transmitter, a tuned alternating current signalreceiving circuit coupled to said shunt and means for applying a portionof the received A. C. signal current from said tuned circuit to awinding of said D. C. receiving relay.

9. A signaling circuit comprising a line, a D. C. telegraph transmitterconnected across said line, a D. C. receiving relay having windings inseries in said line, an inductive shunt circuit connected to the lineterminals of said transmitter, a tuned alternating current signalreceiving circuit coupled to said shunt comprising means for amplifyingthe received alternating current and means for applying an adjustableportion of the amplified current to a winding of said D. C. receivingrelay.

10. A sgnaling circuit comprising a line, a D. C. telegraph transmitterconnected across said line, a D. C. receiving relay having windings inseries in said line, said transmitter being connected to neutral pointsof said relay through a filter designed to suppress A. C. components ofthe D. C. signal having a given frequency, an alternating currentreceiving circuit tuned to signal currents of said given frequency,means for receiving alternating currents of said given frequency in saidtuned circuit through the line windings of the D. C. relay in series andmeans for applying a neutralizing alternating current of said givenfrequency to said D. C. relay. y.

11. In a superposed telegraph system, a pair of line conductors and anartificial balancing line therefor, transmitting and receiving apparatusconnected to said line and artificial line for the two way transmissionof direct current signals thereover, an alternating current channelsuperposed thereon comprising a transmitter at one end of the line and areceiver at the other, the impedance of said artificial line at thefrequency of said alternating current being substantially the same asthe line impedance at said A. C. frequency and means comprising saidartificial line for neutralizing the effect of signals from said A. C.transmitter upon said direct current receiving apparatus.

12. In a combined direct and alternating current telegraph system, aline and an artificial line therefor adapted to balance said line fordirect and alternating current signal frequencies, a direct currentreceiving relay, a direct current transmitter connected to the line andbalancing line through opposed windings of said relay whereby theeffects of currents from the D. @transmitter on said relay neutralizeone another, an alternating current channel superposed upon said linecomprising an A. C. transmitter connected to said line and artificialline in balancing relation through said opposed windings of the D. C.relay.

13. In a combined direct and alternating current telegraph system, aline, an artificial line therefor having an impedance characteristicsimulating that of the line at the frequencies of thedirect andalternating current signals, a direct current transmitter, a directcurrent receiving relay having windings in said line and other windingsin said artificial line connected in opposition to said line windingswith respect to currents from said direct current transmitter and analternating current transmitter connected to send A. C. signal currentsthrough the line and artificial line' windings of said direct currentrelay in opposition.

14. In a combined direct and alternating current telegraph system, aline, an artificial .line therefor having an impedance characteristicsimulating that of the line at the frequencies of the direct andalternating current signals, a direct current transmitter connectedacross said line, an inductive shunt circuit connected to the terminalsof said transmitter, a direct current receiving relay having windings insaid line and other windings in said artificial line connected inopposition to said line windings with respect to currents from saiddirect current transmitter, an alternating current channel superposed onsaid line comprising an alternating current transmitter coupled to saidshunt circuit, whereby A. C. signal currents from said A. C. transmitterpass through the line and artificial line windings of said directcurrent relay in opposition.

15. In a combined direct and alternating current telegraph system, aline, an artificial line therefor having an impedance characteristicsimulating that of the line at the frequencies of the direct andalternating current signals, a direct current transmitter connected tosaid line through filtering means designed to exclude currents of thealternating current signal frequency, an inductive shunt circuitconnected to the terminals of said transmitter, an alternatin currentvsignal transmitter coupled to saidF shunt, a direct 10 current receivingrelay having windings in said line and other windings in said artificialline connected in opposition to said line windings with respect tocurrents from said direct and alternating current transmitters.

16. In a combined direct and alternating current telegraph system, aline, an artificial line therefor havin anV Vimpedance characteristicsimulating that of the line at they frequencies of the direct andalternating current signals, a direct current transmitter connect- -edacross said line, an inductive shunt circuit connected to the terminalsof said transmitter, a direct current receiving relay havin windings insaid line and windings in said artificial line connected in oppositionto said line windings with respect to current from said direct currenttransmitter, capacitive shunts about the windings of said line andartificial line relay windings, and an alternating current signaltransmitter coupled to said shunt circuit, whereby signals from said A.C. transmitter are prevented from caus-A ing operation of said directcurrent relay.

In testimony whereof I aiix my signature. RONALD V. MORGEINSTERN.

